#include <iostream>
#include <vector>
using namespace std;

int main()
{
    int n;
    cin >> n;
    vector<int> cost(n);
    for (int i = 0; i < n; i++)
        cin >> cost[i];

    vector<int> dp(n + 1);

    dp[0] = dp[1] = 0;

    for (int i = 2; i <= n; i++)
        dp[i] = min(dp[i - 1] + cost[i - 1], dp[i - 2] + cost[i - 2]);

    cout << dp[n] << endl;

    return 0;
}